System and method for managing an optical networking service

ABSTRACT

Described are a system and method for managing a service across an optical network over a dedicated circuit between a first and second service termination points. Each service termination point generates a service performance report message. Each service performance report messages has information related to a performance of the service as determined by the service termination point generating the message. The service termination points exchange the service performance report messages over a service management channel to enable an assessment of the performance of the service based on the service performance report messages from both service termination points. Through access to and use of the service management channel, service providers can implement an edge management model or a core management model for measuring the performance of their services with respect to service level agreements governing those services.

RELATED APPLICATIONS

This application claims the benefit of the filing date of co-pendingU.S. Provisional Application, Ser. No. 60/412,135, filed Sep. 20, 2002,titled “Optical Broadband Service Management Framework,” the entirety ofwhich provisional application is incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates generally to optical telecommunications systems.More particularly, the invention relates to a system and method formanaging network services across an optical network.

BACKGROUND

Transport networks of today need to provide cost-effective transport forvarious types of client information, including multi-service trafficranging from synchronous traffic (e.g., DS-1, DS-3, and STS-12) toasynchronous traffic (e.g., IP, Ethernet, and ATM). Traditionally,service providers support such services on transport networks based onsynchronous optical network (SONET) or synchronous digital hierarchy(SDH). Service providers specify the services that they agree to furnishto their customers in contractual service level agreements or SLAs.Often, SLAs provide terms and parameters against which the performanceof the services can be measured. Accordingly, service providers want tomonitor the services that they provide to ensure that each service isperforming in accordance with its corresponding SLA.

Networking technologies, such as SONET, offer service providersoperations, administration, and management (OAM) capabilities formanaging the performance of the transport facility. However, serviceproviders are unable to use these current OAM capabilities to monitorservices across a network because of the diversity of OAM servicemanagement techniques. Some OAM management functions occur at high-levelpacket switching levels such as the network layer (i.e., layer 3 or L-3)and the data link level (i.e., layer 2 or L-2), some occur at low-leveltransport switching such as the physical layer (i.e., layer 1 or L-1)and the optical layer (i.e., layer 0 or L-0), others occur atnetwork-edge service control points, and still others occur at corenetwork elements. Additionally, service providers need to be able tosupport link-based, end-to-end path based, and application-specific OAMmodels. Presently, no single technique exists for transporting, mapping,and accessing relevant service-specific OAM information across thenetwork. To offer multi-services, service providers need a single OAMsolution that can merge different technologies, such asconnection-oriented and connectionless service management technologies.

Further, a service can traverse the networks of multiple carriers.However, OAM information typically does not transmit across handoffpoints between network carriers. As a result, OAM information is notreliably transmitted from one end of the network to another, making itimpossible for a service provider to guarantee the performance andreliability of its service across the network.

Current OAM techniques also do not provide service providers with accessor control points. As a result, OAM information is not accessible at thenetwork locations where the service provider can accurately measure andcharge for its service. In fact, some service providers, such aswholesale carriers, do not have a service edge that it can access tomonitor a service. Another consequence of a lack of control points isthe inability of service providers to isolate and segment faultsadequately for commissioning and reliability purposes. In general, OAMinformation and control are not segmented at demarcation and hand-offpoints, such as at user network (UNI) and network-to-network interfaces(NNI). There is a need, therefore, for a system and method that enableservice providers to monitor the performance of their services moreeffectively than current OAM techniques.

SUMMARY

In one aspect, the invention features a method for managing a serviceacross an optical network over a dedicated circuit between a first andsecond service termination points. A service performance report messageis generated at each of the service termination points. Each serviceperformance report message has information related to a performance ofthe service as determined by the service termination point generatingthat service performance report message. The service performance reportmessage generated by one of the service termination points istransmitted to the other service termination point over a servicemanagement channel to enable an assessment of the performance of theservice based on the service performance report messages from bothservice termination points.

In another aspect, the invention features an optical network forsupporting a service provided by a service provider over a dedicatedcircuit between service termination points. The optical networkcomprises first and second network elements. Each network element isdisposed in the dedicated circuit of the service. The first networkelement sends a message to the second network element over an opticaltransport facility using a service management channel capable ofcarrying the message across a network-to-network interface. The messagesconvey information related to a performance of the service over thededicated circuit.

The invention also features a network element connected at one end of adedicated circuit used to carry customer traffic associated with aservice. The network element comprises a client interface receivingclient signals from a client network. A service management channelentity derives from the client signals information related to aperformance of the service and generates a message in response to theservice performance information. A transport interface, for mapping andadapting the client signals to an optical transport facility, transmitsthe message to a network element at the other end of the dedicatedservice over a service management channel capable of carrying themessage across a network-to-network interface.

In yet another aspect, the invention features a network elementconnected between service termination points located at opposite ends ofa dedicated circuit used to carry customer traffic associated with aservice. The network element comprises a transport interface receivingcustomer traffic associated with the service. A service managementchannel entity processes the customer traffic received by the transportinterface to access service performance information stored in a servicemanagement channel of the transport facility by one of the servicetermination points.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further advantages of this invention may be betterunderstood by referring to the following description in conjunction withthe accompanying drawings, in which like numerals indicate likestructural elements and features in various figures. The drawings arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention.

FIG. 1 is a diagram of an embodiment of an optical network including afirst network element in communication with a second network elementthrough a network intra-connect element over a transport facility.

FIG. 2 is a diagram of an embodiment of the service network of FIG. 1 inwhich the first and second network elements are edge service switches.

FIG. 3 is a diagram of another embodiment of a service network of FIG. 1in which one of the first and second network elements is an edge serviceswitch and the other is a core service switch.

FIG. 4 is a block diagram of an embodiment of an edge service switch.

FIG. 5 is a block diagram of an embodiment of a core service switch.

FIG. 6 is a diagram illustrating various loopback conditions useful forconnectivity verification and fault isolation.

FIG. 7 is a diagram of a SONET synchronous transport signal (STS) frame.

FIG. 8 is a diagram of a format for a POH byte used to implement oneembodiment of the service management channel of the invention.

FIG. 9 is a diagram of a format of an embodiment of a service PRM superframe.

FIG. 10 is a diagram of a format of an embodiment of an Ethernet servicePRM super frame.

FIG. 11 is a diagram of a format of an embodiment of a Fibre Channelservice PRM super frame.

FIG. 12 is a diagram of a format of an embodiment of a command message.

FIG. 13 is a diagram of a format of an embodiment of an Ethernet servicereport message generated by an edge service switch in response to acommand message.

FIG. 14 is a diagram of a format of an embodiment of a Fibre Channelservice report message generated by an edge service switch in responseto a command message.

FIG. 15 is a diagram of a network configuration of a network supportedby a single carrier over a single transport domain.

FIG. 16 is a flow diagram illustrating an embodiment of a process forcommissioning an Ethernet Private Line service for a single carrier overa single transport domain in accordance with the principles of theinvention.

FIG. 17 is a flow diagram illustrating an embodiment of a process fordiagnosing service degradation in accordance with the principles of theinvention.

FIG. 18 is a flow diagram illustrating an embodiment of a process foridentifying and alerting a customer potentially affected by degradationin service.

FIG. 19 is a diagram of a network configuration of a network carrying aservice supported by multiple carriers over multiple transport domains.

FIG. 20 is a flow diagram illustrating an embodiment of a process forcommissioning a Private line service involving multiple carrier networksin accordance with the principles of the invention.

DETAILED DESCRIPTION

The present invention features an optical broadband services (OBS)framework that combines service-specific management withtransport-facility management over a service management channel. Anoptical network configured in accordance with this framework enables anetwork operator to evaluate and manage the performance of a service.Service, as used herein, is a guarantee of transport of customer-offeredtraffic with specific performance commitments. The service provider andpossibly one or more carriers transport the customer-offered trafficover the optical network on a dedicated circuit betweenservice-termination points. Network elements at theseservice-termination points measure the performance of thecustomer-offered traffic and exchange the performance metrics across thenetwork. Service performance metrics are based on trafficcharacteristics, not container (i.e., facility) characteristics.

The network operator accesses the performance metrics from a networkelement at a service termination point (i.e., at a network edge) or atan interior point in the network. In accordance with the principles ofthe invention, the accessed network element is capable of communicatingservice-related messages over the service management channel. From theinformation gathered at the access point, the network operator is ableto determine whether the performance of the service is complying withparameters set forth in a service level agreement (SLA). The networkoperator can also perform other service-related operations, such aservice commissioning and testing.

The OBS framework can support a variety of services. Examples ofsupported services include, but are not limited to,

a) asynchronous broadband private line services, such as DS0, DS1, DS3,E1, and E3 private line,

b) SONET/SDH services, such as SONET/SDH private line, OC-n (where n=3,12, 48, or 192), STM-n (where n=1, 4, 16, or 48), and traditionalsynchronous payload envelopes (SPEs) including synchronous transportsignals STS-1 , STS-3c and VC4,

c) local area network (LAN) and storage area network (SAN) services,such as Ethernet Private Line (full and variable rate using GenericFraming Procedure—Full/Transparent (GFP-F/T)) and Storage Private Lineservices such as Fiber Channel Private Line (Full and Variable Rateusing GFP-F/T), and

d) managed wavelength services, such as Open Private Line(high-definition television (HDTV), SONET/SDH, LAN/SAN), Transparent 8B/10 B Private Line services such as Enterprise System Connection(ESCON), DVB-ASI, FC-100, 1 GbE, ISC, and OC-n transparency (2.5 G and10 G), such as ODU-OTN networking and G.Modem (sync TPM).

The following description refers primarily to Synchronous OpticalNetwork (SONET) as the optical infrastructure over which the servicemanagement channel of the invention carries service-related messages,but the invention applies also to other optical standards, such asSynchronous Digital Hierarchy (SDH) and Optical Transport Network (OTN).

FIG. 1 shows a general embodiment an optical network 10 constructed inaccordance with the principles of the invention. A service provider orcarrier uses the optical network 10 to support a service purchased by acustomer under terms governed by an SLA. Customer traffic pertaining tothe service travels from one end of the network 10 to another end of thenetwork 10 over a dedicated circuit or path 12. As used herein, the termend-to-end refers to the service or service path (i.e., client-to-clientor customer-to-customer). The path 12 includes a first network element14 in communication with a second network element 18 through a networkintra-connect element 20. The network elements 14, 18 exchangeservice-related messages with each other through a service managementchannel (SMC) 24 over a transport facility 26.

Each network element 14, 18 is in communication with a respectiveinterface 22, 28 and includes respective software 32, 36 for performingthe particular functions of that network element and for processing theservice-related messages conveyed by the SMC 24. Types of networkelements that are configured to communicate service-related messagesover the SMC 24 include service demarcation points (i.e., servicetermination or end points) and carrier hand-off points (i.e., interiornetwork devices). Implementations of the SMC 24 include using 1) thepath overhead (POH) of SONET STS frames or of SDH virtual containers(VC), and 2) client management frames of Generic Framing Procedure(GFP), as described in more detail below.

The network intra-connect element 20 primarily performs facilityswitching functions for traffic between the network elements 14, 18.Although in the path of the service, the network intra-connect element20 does not process the service-related messages in the SMC 24. Similarto digital cross-connects systems, the network intra-connect element 20functions without regard to the type of customer traffic passingthrough. The transport facility 26, generally, is a transport mechanismfor carrying the communications among the network elements 14, 18, 20and interfaces 22, 28. Although a transport facility is typically withinthe network of a single service provider or carrier, the transportfacilities of multiple carriers may be needed to support the servicebetween service termination points. Communication over the transportfacility 26 occurs according to a standard for synchronous datatransmission over fiber optic networks, such as SONET, SDH, or OTN.

During operation, the network elements 14, 18 use the SMC 24 to performvarying degrees of service processing. The SMC 24 enables a networkoperator of a service provider, who has access to one of the networkelements 14, 18, to manage, monitor, and test the services supported bythe service provider, as described in detail below. Service processingincludes 1) service monitoring and managing; 2) service commissioningand service connectivity testing; and 3) traffic switching based onservice-specific parameters (i.e., protection switching), which aredescribed in more detail below. The capabilities provided by the SMC 24can be supplemental to existing OAM functions for supporting theservice, e.g., MAC OAM frames and GFP OAM frames, and facility-basedconnection management capabilities, e.g., Tandem Connection Monitoring(TCM) and Internet Protocol Performance Metrics (IPPM). TandemConnection Monitoring, for example, uses a facility channel (i.e., theN1 byte of the POH) to manage network facilities that support theservice.

Edge Management Model

FIG. 2 shows an embodiment of the optical network 10, in which the firstand second network elements 14, 18 are service termination points(hereafter, each referred to as an edge service switch or an ESS). AnESS is a network device that interfaces with a client network,interprets client signals, and performs carrier network adaptationfunctions and service mapping functions. Depending upon the type ofservice supported, client signals may be protocol-data-unit- orPDU-oriented, such as IP/PPP or ETHERNET MAC, block-oriented code, suchas Fibre Channel or ESCON, or a constant bit rate stream. Generally,edge service switches embody User Network Interfaces (UNIs). In oneembodiment, the ESSs 14, 18 both belong to the same carrier network. Inanother embodiment, the ESS 14 is part of a different carrier networkthan the ESS 18.

Through the respective interfaces 22, 28, each ESS 14, 18 communicateswith the equipment of the client network. The point at which each ESS14, 18 communicates with the respective interface 22, 28 is denoted inFIG. 2 as a service demarcation point. Each demarcation point representsa point in the network 10 at which the customer is granted access to thenetwork 10 and to the service being offered by the service provider. Asused herein, edge-to-edge refers to the service or service path within asingle carrier (i.e., from demarcation point to demarcation point).

Through execution of the respective software 32, 36, each ESS 14, 18performs service mapping functions and network adaptation functions.Service mapping functions include 1) providing service (i.e., customeror client) interface and interface options, 2) performing serviceencapsulation, 3) service monitoring, and 4) providing protectionoptions. Network adaptation, in general, reshapes traffic fromhigher-layer client signals for transmission over the transport facility26. More specifically, network adaptation functions include 1) producingcommon network containers (i.e., common networking attributes offered bythe network technology), 2) aggregating and transporting signals, 3)establishing an end-to-end path/connection, 4) performing facilitymanagement, and 5) performing network element management. For example,network adaptation for SONET uses STS-n payload envelopes (SPE) tomanage connectivity and to provide multiplexing, aggregation, andoverhead information for networking and management.

During operation, each ESS 14, 18 generates and transmits serviceperformance report messages (PRMs) over the SMC 24 and performs servicemonitoring in accordance with the principles of the invention.Performance report messages are scheduled messages; that is, each ESS14, 18 generates a PRM periodically (e.g., once per second). In general,PRMs inform the source ESS (i.e., transmitter of optical signals) oftransmission errors received by the sink ESS (i.e., recipient of opticalsignals) and communicate service-specific information.

To generate the PRMs, each ESS 14, 18 gathers service performancestatistics and facility (i.e., link or transport) performance statisticsand incorporates both types of statistics into the periodicallygenerated PRMs. For example, for a typical Ethernet private lineservice, facility/link performance metrics can include errored framedseconds (EFS) and severely errored frame seconds (SEFS), and servicestatistics can include packet throughput, packet access bandwidth, andpacket drop rate. Examples of format and content of PRMs are describedbelow.

When transmitting PRMs, the source ESS maps and adapts the servicesignal, including the PRMs, into an optical signal to be transportedover the optical facility 26. The source ESS places the PRMs into theSMC 24 of the optical signal. Preferably, the SMC 24 is implemented inthe POH of the SDH VC or SONET SPE (i.e., at L-1). In anotherembodiment, the SMC 24 is implemented at the GFP layer.

The source ESS does not target the PRMs to any remote network element inparticular. The PRMs generated by ESS 14 traverse the transport facility26 and are received by the ESS switch 18. Similarly, the PRMs generatedby the ESS 18 traverse the transport facility 26 and are received by theESS 14. The ESSs 14, 18 store the PRMs received from the other ESSduring a specified period, and collectively analyze those PRMs. Thus,each ESS 14, 18 possesses service performance data from both end pointsof the service and can monitor the performance of the service bycomparing the statistics gathered at both service ends.

This service monitoring capability enables service providers to apply an“edge management model” to manage its services. More specifically, aservice provider with access to one of the ESSs 14, 18 can measure theperformance of the service against terms set forth in the SLA with thecustomer of that service. The service provider can be assured of theservice's compliance with the SLA or, in the event of a degradingservice, can take proactive steps to comply with the SLA.

Core Management Model

The service typically passes over the transport facility 26 of theservice provider through a core network in the optical network of theservice provider or of another carrier. In accordance with theprinciples of the invention, a network element at an intermediate pointin the service path can monitor the service and facility performancemetrics. FIG. 3 shows another embodiment of an optical network 10′ inwhich the first network element 14 is an ESS and the second networkelement 18′ is situated at an intermediate point between servicetermination points. Here, the ESS 14 is one of the service terminationpoints and a second service termination point is not shown. Edge serviceswitches are described above in connection with FIG. 2.

The intermediate network element 18′, hereafter referred to as a coreservice switch or CSS, is capable of processing information conveyed bythe SMC 24 and combines facility connect functions with serviceprocessing functions. The CSS 18′ accomplishes these functions throughthe execution of the software 36′. Service processing functions of thecore service switch 18′ include 1) service management, 2) servicecommissioning, 3) service monitoring, 4) service testing, and 5) localand remote operations, administration, maintenance and processing(OAM&P).

The CSS 18′ communicates with a network inter-connect device 28′situated at a point in the network 10′ referred to as a network orcarrier handoff. The network handoff is a point at which the customertraffic traverses different transport facilities or different carriers.Typically, the network inter-connect device 28′ has open standard, L-1aggregated (OC-n), and L-2 aggregated interfaces (I/F), and performslink management and intermediate service and facility monitoring.

The CSS 18′ serves as a portal for monitoring the service between theservice termination points, and enables service providers to apply a“core management model” for the management of its services. Because theCSS 18′ is an intermediate point in the service path, the networkoperator can use the CSS 18′ to intercept the service PRMs generated bythe ESSs and collect historical performance information (i.e., servicemonitoring). Like the ESS 14, the CSS 18′ can accumulate and store theinformation for a predetermined length of time. With the accumulatedinformation, a network operator can evaluate the performance of theservice against an SLA. Also, the network operator can use the CSS 18′as a portal to perform service commissioning, to manage the ESSs, and topotentially switch traffic based on the service information. Someservice providers may want to support the edge management model, whereasothers may want to support the core management model, and still otherservice providers may employ both.

A network can have more than one interior network element (such as theCSS 18′) that can process information in the SMC 24. These interiornetwork elements serve as a plurality of performance monitoring pointsat different locations along the network. Consequently, a networkoperator with access to the various monitoring points can localize anerror (i.e., fault isolation) occurring within the network by examininginformation gathered at each of the monitoring points.

During operation, the CSS 18′ of the optical network 10′ performsservice monitoring in accordance with the principles of the invention.An exchange of PRMs occurs between a near-end switch (here, the ESS 14)and a far-end edge service switch (not shown). As described above inconnection with FIG. 2, the SMC 24 carries the PRMs between the servicetermination points. In the exchange between service termination points,the PRMs pass through the CSS 18′. The CSS 18′ has a protocol stack thatcan process the SMC 24 and forward received signals towards theirdestinations.

To support core management, each ESS uses all STS paths that make up theconnection to dispatch the service PRMs. This simplifies monitoring ofPRMs at the CSS 18′, especially during protection events, because theCSS 18′ needs to monitor only one path (per service). The CSS 18′ canselect or deselect which paths are being actively monitored at any givenpoint in time. Like the ESS 14, the CSS 18′ can extract the messagingfrom the SMC 24. In the case of the CSS 18′, the contents of the SMC 24are mirrored (i.e., a drop and continue function) and passed to aservice monitoring function (i.e., a software-based capability possessedby switches 14, 18′). Accordingly, a service provider or carrier withaccess to the CSS 18′, like a service provider with access to the ESS14, has access to PRMs from both service termination points. Thus, theservice provider can monitor the service performance by comparingstatistics gathered at both service termination points and measure theperformance of the service against the SLA with the customer of thatservice.

To commission or test the service, the ESS 14 and the CSS 18′ of theoptical network 10′ can issue service commands over the SMC 24 inaccordance with the principles of the invention. In one embodiment, theCSS 18′ and ESSs can initiate a service command, but only ESSs canrespond to a service command. The network operator inserts servicecommands (e.g., loopback, service query) into the SMC 24 at either theESS 14 or at the CSS 18′, and directs the service command to one of theESSs.

Edge Service Switch

FIG. 4 shows a functional diagram of an ESS 100 of the invention. Ingeneral, the ESS 100 is an optical network element that relays clientsignals (like a digital cross-connect) and performs SMC functions. TheESS 100 includes a supervisory management and control system 104, amanagement component 108, and a user component 112. A network operatorinserts commands into the SMC 24 through the supervisory management andcontrol system 104.

The management component 108 includes software for performing SMCprocessing, and the user component 112 includes software for switchingclient signals (i.e., customer-offered traffic related to the service)to the appropriate optical transport port. The user component 112corresponds to the facility-switching portion of the network element ESS100. More specifically, the user component 112 logically includes a linkentity 136, a relay entity 140, and an optical entity 144. The linkentity 136 performs link-method dependent functions and passes linkstatistics (e.g., FCS errors) to the management component 108,specifically a SMC OAM Source/Sink (SOS) agent 116. Client signals passthrough the relay entity 140 for forwarding (i.e., a switching process)to the optical entity 144. The switching process passes packet countmetrics (e.g., frames received, sent, throughput) to the SOS agent 116.Also passed to the SOS agent 116 are SMC commands. The optical entity144 performs optical-method dependent functions, such as networkadaptation (e.g., GFP, STS) and service mapping.

The management component 108 logically includes the SOS agent 116,service-link agent 120, a SMC-link agent 124, a service-statistics agent128, and a transport-statistics agent 132.

The SOS agent 116 performs functions such as 1) processing all SMCcommands and responses, 2) translating commands into network elementactions (e.g., loopback), 3) generating scheduled service PRMs andunscheduled priority messages based on reads and event triggers from thedatabases, 4) extracting statistics from SMC messages and writing suchstatistics to the appropriate database, and 5) extracting far-endstatistics from service OAM messages and writing such statistics to theappropriate database. To perform such SMC operations, the SOS agent 116interacts with the link agents 120, 124 and the statistic agents 128,132. The SOS agent 116 also interfaces with the supervisory managementand control system 104 and manages interactions between service link OAMsignals and the SMC 24.

The service link agent 120 handles the termination of service OAMmessages and schedules service OAM messages; the SMC link agent 124handles the termination of SMC messages and schedules SMC messages to bedispatched. The SMC link agent 124 also extracts the contents from theSMC 24 and sends the contents to the SOS agent 116.

The service statistics agent 128 maintains a repository or database 130of client-specific link statistics. The service statistics agent 128 caninteract with the SOS agent 116 to process service PRMs that haveinformation derived from the service statistics. Examples of servicestatistics (for an Ethernet client, for example) are frame codingsequence (FCS) errors and coding violations. The transport-statisticsagent 132 maintains a repository or database 134 of opticaltransport-specific statistics. The transport statistics agent 132 caninteract with the SOS agent 116 to process service PRMs that haveinformation derived from the transport statistics. The service-specificdatabase 130 stores information such as L-2 statistics (e.g., IEEE 803.1MIB) and link OAM (e.g., IEEE P802.3ah EFM OAM) information. These givenexamples are specific to an Ethernet service. The type ofservice-specific information depends upon the type of service beingmonitored. The transport database 134 stores information such as GFPstatistics (e.g., discarded frame counts), STS statistics (e.g., B3error count) and equipment statistics (e.g., GFP ASIC integrityfailures).

Core Service Switch

FIG. 5 shows a functional diagram of a CSS 100′ of the invention. Likethe ESS 100 of FIG. 4, the CSS 100′ is also an optical network elementthat relays client signals and performs SMC functions. The CSS 100′includes a supervisory management and control system 104′, a managementcomponent 108′, a user component 112′, and maintains databases 130′,134′ similar to those corresponding databases maintained by the ESS 100.In general, the functionality of the control system 104′, managementcomponent 108′, and user component 112′ are similar to the correspondingfeatures of the ESS 100, with the following noted differences.Statistics are collected at the edges of the network, not in the networkcore. Accordingly, the management component 108′ of the CSS 100′ lacksstatistics agents, such as the service-statistics agent 128 and thetransport-statistics agent 132 of the ESS 100. Also, the CSS 100′forwards traffic between optical transport facilities or networks, incontrast to the ESS 100 which interfaces between the client link and thetransport facility. Accordingly, the user component 112′ of the CSS 100′includes an optical entity 144′ and the management component 108′includes an SMC link agent 124′ for each transport interfaced. Further,the CSS 100′ lacks a service link agent and link entity, such as theservice link agent 120 and link entity 136 of the ESS 100.

SMC-Enabled Capabilities

Generally, the SMC carries three types of messages: 1) priority codemessages, 2) command-and-response messages, and 3) service PRMs.Priority code and command-and-response messages are unscheduledmessages, whereas service PRMs are scheduled messages. With the use ofthese messages, a network operator with access to an SMC-enabled ESS orCSS can perform a variety of functions, some of which have been brieflydescribed above. The functions include two broad categories: 1) servicesurveillance and 2) service commissioning and testing.

The first category, service surveillance, has two components: alarm orstatus monitoring and performance monitoring. Alarm or status monitoringis a process of tracking failure events to build an understanding of theoverall transmission performance of a network element. Performancemonitoring is a process of continuous collection, analysis, andreporting of performance data associated with the transmitting networkelement.

With regard to alarm or status monitoring, the first component ofservice surveillance, one capability of the SMC is for carrying alarmsignals. Categories of alarms carried over the SMC include networkfacility alarms and service alarms. For a service carried over a SONETnetwork, SONET maintenance signals can be used. For example, a remotealarm indication (RAI) signal and an alarm indication signal (AIS) areexamples of SONET alarm signals that can be transmitted over the SMC 24.RAI signals travel upstream (i.e., towards the source of the incomingsignal) when SONET terminal equipment determines that the incomingsignal is effectively lost. AIS signals travel downstream to a SONETnetwork element upon a loss of incoming SONET signal (e.g., loss ofsignal or LOS, Internal Equipment Failure), or when an action occursthat can cause a service disruption (e.g., a loopback). The AIS isremoved when the triggering condition terminates.

The SMC 24 can also be used to carry service-specific alarm signals.Examples of service alarms include a client signal failure (CSF) signaland a service remote fault (SRF) signal. When an ESS detects a loss ofclient signal (e.g., because of a customer link fiber cut), the ESStransmits downstream a CSF signal to the far-end ESS. Upon receiving theCSF signal, the far-end ESS raises a far-end client signal fail alarm.After the loss of client signal event clears (e.g., because the cutfiber is repaired), the near-end ESS stops transmitting the CSF signal,the LOS alarm at the near-end is cleared, and then the far end clientsignal fail alarm at the far-end edge service switch is cleared.

Upon detecting a network adaptation or mapping failure (e.g., the lossof GFP frame delineation), an ESS transmits an SRF signal upstream tothe far-end ESS. The near-end ESS then periodically generates SRFsignals destined to the far-end ESS. Upon receiving an SRF signal, thefar-end ESS raises an alarm and performs procedures to shut down thecustomer link. When the network adaptation or mapping failure clears,the near-end ESS stops sending SRF signals to the far-end ESS. As aresult, the near-end and far-end ESS re-establish their respectivecustomer links.

With regard to service performance monitoring, the second component ofservice surveillance, a capability of the SMC is for carrying theperiodic exchange of service PRMs between service termination points(i.e., the ESSs). The format of these service PRMs is service specific,and the contents of the service PRMs are designed to support thegoverning SLA. Intermediate points within the network, i.e., CSSs,monitor end-to-end status of the service based on the serviceperformance information in these service PRMs.

Counts of certain events are accumulated during each interval. Theseevent counts serve as the performance information put into a PRM.Examples of types of events for inclusion in a service PRM are serviceerror events, transmitted and received packets, packet throughput,service status (e.g., in-service, out-of-service), and serviceprotection events. The particular events captured are identified asthose that support a determination of whether the service is performingin accordance with the particular SLA.

The second category of SMC-provided capabilities, service commissioningand testing, features processes by which the network operator canperform out-of-service testing, such as testing service connectivity,checking service configuration, and provisioning a service at a remotesite. Service commissioning functions include loopback and servicediagnostics. Network operators can use the SMC to perform loopbackoperations between the network of the service provider and the customerinterface, or between carrier hand-off points. As a consequence, networkoperators can verify sectional connectivity of the network.

The loopback function, for instance, permits verifications ofconnectivity at various points along the dedicated path of the servicebefore activation of the service to determine whether the network cantransport packet information. In addition, in the event of serviceinterruptions, the loopback function can be used to check connectivityto isolate failure points. FIG. 6 illustrates the various types ofloopback conditions that a network operator can configure using the SMCto verify connectivity or perform fault isolation. As shown, the ESS 14is in communication with the client interface 22. The ESS 14 has servicereceive-transmit interfaces 150 in communication with the clientinterface 22 and an OC-n facility interface 154 in communication withthe transport facility 26. Types of loopback conditions shown are clientloopback, link loopback, payload/path loopback, and line loopback.

Client loopback occurs at the client interface (i.e., the customerequipment) 22. Link loopback occurs at the client side of the servicereceive-transmit interfaces 150. For link loopback, only the payload isreturned (i.e., looped back to the sender). Payload/path loopback occursat the network side of the service receive-transmit interfaces 150, andline loopback occurs at the transport facility 26. With these variousloopback options, a network operator at the CSS 18′ (FIG. 3) can signalthe ESS 14 to enter a loopback state over the SMC 24. When in thisstate, the ESS 14 loops the signal from the transmission path to thereceive path. Consequently, the transmission of the carrier signal tothe client interface 22 experiences an interruption.

Also before service activation, the network operator can verify that theservice configurations at the ESS are consistent with each other. Byquerying each service termination point (i.e., ESS) over the SMC 24, thenetwork operator uses service diagnostics to learn the service type(e.g., Ethernet, Fibre Channel, OC-n), service configuration information(e.g., auto-negotiation parameters, link policing mode (i.e., pauseenabled or disabled), port speed, and transmission mode (i.e., simplexor duplex)), and SLA parameters (e.g., EFS, SEFS committed informationrate or CIR, peak information rate or PIR). To support such servicediagnostics, the SMC 24 carries command-and-response messages.

Service Management Channel (SMC) Implementations

Implementations of the SMC include 1) a byte in the path overhead (POH)of SONET STS frames (or of SDH VC frames), and 2) client managementframes of Generic Framing Procedure (GFP).

Path Overhead (POH) Implementation of SMC

FIG. 7 shows a SONET frame format, which is based on an STS-1 frame 170.The STS-1 frame 170 includes of a transport overhead 174 and asynchronous payload envelope (SPE) 178. The STS-1 frame has 810 bytesorganized as 9 rows of 90 bytes. The first three bytes of each row(i.e., the first three columns of the STS-frame) are the transportoverhead 174; the remaining 87 columns are the SPE 178. The first column182 of the SPE 178, consisting of nine bytes, is the path overhead(POH). Path terminating equipment (e.g., the edge service and coreservice switches) use the POH to communicate various information. Eachbyte of the POH conveys a different type of information. In oneembodiment (SONET), the SMC 24 is implemented in the Z3 byte of the POH(for SDH, the corresponding byte of the POH is the F3 byte). Anadvantage of using the POH for the SMC 24 instead of using the transportoverhead (e.g., a byte in the line overhead or LOH or in the sectionoverhead or SOH) is that information in the POH traversesnetwork-to-network interfaces, whereas information in the LOH and SOHdoes not. A byte or bytes of the POH, other than the Z3 byte, can beused for the SMC 24 without departing from the principles of theinvention.

FIG. 8 shows an example assignment of bits in the POH byte 200 used toimplement the SMC 24. The particular bit assignments described hereinare for purposes of illustration. One skilled in the art will recognizethat different bit assignments can be used to practice of the invention.Eight bits are used to define a two-bit service status field 204, afour-bit service PRM field 208, and a two-bit command-and-response field212. The bits are labeled 0-7, with bit 0 least significant bit. Bits 0and 1 define the two-bit service-status field 204. Table 1 correspondingservice status for each combination of bit values in the service-statusfield 204.

TABLE 1 Bit Service values Status 00 Active 01 Degrade 10 Fail 11Controlled

An active service status indicates that the service is performingaccording to metrics set forth in the governing SLA. The service has adegrade status when the service is experiencing a degraded level ofconformance to the SLA. In this case, the service is functioningproperly, but encountering anomalies that are affecting the service. Afail status indicates SLA violations are occurring because of problemsencountered at network elements of the carrier.

Edge service switches determine the value stored in the service-statusfield 204. Each ESS measures the service performance against serviceperformance thresholds configured at that ESS. These performancethresholds are based on an SLA. The value placed in the service-statusfield 204 reflects the performance of the service against theperformance thresholds. Each ESS also corelates near-end PRMs withfar-end PRMs to produce end-to-end service performance reports. Coreservice switches continuously monitor the service-status field 204. Upondetecting a service degrade or fail condition, the service providermonitoring the service through the CSS can take reactive or proactiveactions. These actions are taken by using the command-and-responsesub-field, described in more detail below.

Bits 2 through 5 define the four-bit performance report message field208. As described in more detail below, one embodiment of a performancereport message comprises a fixed-size 32-byte super-frame. An STS-1frame is transmitted every 125 us, and 4 bits of the PRM with each STS-1frame 170. Accordingly, a complete PRM is transmitted in 8 ms and 125PRMs in one second. The information stored in each PRM repeats in eachtransmission until changed by the ESS generating the PRM.

Bits 6 and 7 define the two-bit command-and-response field 212. Thesignaling format is comprised of messages that use a subset of the LinkAccess Protocol—Channel D (LAPD) protocol. This field 212 supports a 16Kbps message-oriented signaling format and bit-oriented signalingformat.

FIG. 9 shows an exemplary embodiment of a general format of a 32-byteservice PRM super frame 220, including a frame-alignment-signal field224, service-specific fields 228, and a frame-coding sequence or FCSfield 232. Different formats than the one described herein can be usedto practice of the invention. Bytes 0 through 2 comprise the framealignment signal field. The frame alignment signal identifies thebeginning of the PRM super frame 220. This 3-byte field has ahexadecimal value of FF FF FE. To ensure that a data pattern thatmatches the frame alignment signal does not occur within the body of thesuper frame 220, bits with a zero value are inserted at variouspositions in the super frame. For example, bit 7 of bytes 5, 8, 11, 14,17, 20, 23, 26, and 29 are not considered part of the service-specificfields 228 and are always set to zero. No bit stuffing occurs whentransmitting information in the super frame 220.

The service-specific fields 228 have a sequence-number (SeqID) field236, a service-label field 240, a service remote-fault indication (RDI)field 244, a client-signal-failure field (AIS) 248, service-state field(S) 252, a loopback status (LpBk) field 256, and a service sub-statesfield 260. The sequence-number field 236 is an eight-bit fieldcontaining the sequence number identifying the super frame. In oneembodiment, the sequence number ranges from 0 to 124, corresponding tothe one hundred twenty-five super frames transmitted per second. A valueof 0 indicates the start of a new second. The value in the fieldincrements by 1 for each subsequent super frame.

The service-label field 240 is a 1-byte field. A set of service labelscompose the service identifier. In one embodiment, the values stored inthe service label field 240 for the first 32 transmitted super framesproduce the service identifier. The service-remote-fault field 244 is a1-bit field indicates whether a network adaptation failure (e.g., a GFPdelineation error) has occurred at the ESS. The client-signal-failurefield 248 is a 1-bit field indicating whether a signal failure occurredbetween the customer equipment and the ESS. The service-status field 252is a 1-bit field that indicates whether the service is in-service(active) or out-of-service (deactivated). For example, a value of 0indicates an active service, a value of 1 indicates deactivated. Theloopback-status field 256 is a 4-bit field that indicates whether thefar-end ESS is in loopback. Table 2 shows the correspondinginterpretations for certain combinations of bit values in theloopback-status field 256.

TABLE 2 LpBk value Interpretation 0000 Loopback Deactivated 0001 ClientLoopback active 0010 Link Loopback active 0100 Payload/path Loopbackactive 1000 Line Loopback active

The service sub-state field 260 provides additional information aboutthe status of the service. The interpretation of the value in theservice sub-state field 260 depends upon whether the service isin-service or out-of-service (as indicated by the service state field252) Table 3 and Table 4 below provide exemplary lists of in-service andout-of-service service sub-states, respectively, corresponding to thefour-bit value in the service-status field 260. The particular servicesub-states described therein are simply examples. One skilled in the artwill recognize that different service sub-states and different valueassignments can be used to practice of the invention.

TABLE 3 SRV-SS value In-service sub-state 0000 Normal (NR) ESS isexhibiting normal in service behavior. Capable and allowed to provideall service functions. 0001 Abnormal (ANR) ESS is allowed to perform allprovisioned service functions, but is capable of performing only partthese functions or of performing these functions at a degraded level.0010 Restricted (RST) ESS is capable of performing all of itsprovisioned service functions but is intentionally suspended fromperforming part (but not all) of these functions. 0011 Abnormal andRestricted (ANRST) ESS is capable of performing only part of itsprovisioned service functions or of performing these functions at adegraded level. ESS is also intentionally suspended from performing partof these functions.

TABLE 4 SRV-SS value Out-of-service sub-state 0000 Autonomous (AU) ESSis incapable performing any of its provisioned functions, and there isno external administrative restriction inhibiting the entity fromperforming these functions. 0001 Management (MA) ESS is intentionallysuspended by the external management command from performing all of itsprovisioned functions. 0010 Building (MA-BLD) ESS is not yet in-serviceand is in a partial state of readiness to provide service to a customer.0011 Testing (MA-TST) ESS is built and potentially ready for service,but has not yet been tested. 0100 Ready (MA-RDY) ESS ready, but nocustomers have been assigned to use this ESS yet. 0101 Tear-Down(MA-TRDN) ESS not yet back to the installed dormant or potential state.0110 Autonomous and Management (AUMA) ESS is incapable from performingany of its provisioned service functions, and at the same time has beenintentionally suspended from performing all of its provisioned servicefunctions. 0111 Autonomous and Restricted (AURST) ESS is incapable ofperforming any of its provisioned functions and at the same time beingintentionally suspended from performing part of its provisionedfunctions. 1000 Management and Abnormal (MAANR) ESS is operationallycapable of performing only part of its provisioned service functions orat a degraded level, and at the same time is intentionally suspendedfrom performing all of its provisioned functions.

The other service-specific fields in the super frame 220 are determinedby the particular service. Once per second, this service-specific PRMinformation becomes updated. When the service is deactivated, each ESScontinues to dispatch service PRMs. These PRMs have information for thebyte 5 service indicators (i.e., SRV-RDI, SRV-AIS, SRV-S, and LpBkstatus field), but no service performance report information.

FIG. 10 shows an embodiment of a super frame format 220′ for an Ethernetservice PRM. One of the bytes of the service-specific information fields228′ has a service-type field 270 and an errored-frame-second (EFS)field 274. Other service-specific fields 228′ are a frame-throughputfield 278, a frames-transmitted field 282, a frames-received field 286,and a frames-dropped field 290.

The service-type field 270 has four bits for representing the type ofservice with which the service PRM is associated. Table 5 shows thecorresponding service type for each combination of bit values. Oneskilled in the art will recognize that other service types can berepresented than those shown.

TABLE 5 Service Type value Interpretation 0000 Reserved 0001 OC-n 0010Ethernet 0011 Fibre Channel 0100 Transparent 0101 Ds-n 0110–1111Reserved

The EFS field 274 is a 1-bit field indicating whether a frame error hasoccurred within a one-second interval. The percentage of framesdispatched to the network-facing interface (with respect to the CIR) isstored in the 7-bit frame-throughput field 278 (i.e., byte 8 of thesuper frame 220′). The frames-transmitted field 282 is a 30-bit field(in bytes 9 through 12) containing the number of Ethernet framestransmitted out of the customer-facing interface during the previousone-second interval. Bit 7 of the byte 11 is a zero bit. Located inbytes 13 through 16, inclusive, the frames-received field 282 is a30-bit field containing the number of Ethernet frames received by thecustomer-facing interface during the previous one-second interval. Bit 7of byte 14 is a zero bit. The number of Ethernet frames that weredropped at the customer-facing interface during the previous one-secondinterval appears in the frames-dropped field 290, a 30-bit field locatedin bytes 17 through 20, inclusive. Bit 7 of byte 17 and byte 20 are zerobits. The reserved fields can have network-side service performancesmetrics.

FIG. 11 shows an embodiment of a PRM super frame 220″ for a FibreChannel service. Many of the fields in the Fibre Channel PRM are thesame as those defined for the Ethernet PRM 220′, such as the byte 5service indicators, a service-type field and an errored frame second(EFS) field and the service sub-status field. The operations of thesefields are the same as those defined for the Ethernet PRM. Unique to theFibre Channel in the service-specific fields 228″ is a buffer-to-buffercount (BBC) field 294, which contains a buffer-to-buffer count of theESS at the end of a previous one-second interval. It is to be understoodthat the principles of the invention apply also to other types ofservices than those described, such as, but not limited to, OC-nservice, DS-n service, and Managed Wavelength (transparent) service.

As described above, the command-and-response field 212 (FIG. 8) supportsbit-oriented and message-oriented signaling. One type of message thatuses bit-oriented signaling is a priority message. Priority messages donot elicit a response message. An embodiment of a format for prioritymessages is, in binary,

0xxxxxx0 11111111, where x indicates either a zero or one bit value. Therightmost bit is transmitted first. The string of eight consecutive “1”bits represents an abort signal for LAPD that permits unscheduledmessages to interrupt the processing of scheduled messages. The six“x”-bits are a priority code that denotes the command conveyed by thepriority message (64 different priority codes are possible).

Table 6 below shows an exemplary set of priority codes. Fewer, more, ordifferent priority codes and commands can be used to practice theinvention than those described in Table 6.

TABLE 6 Priority Code Command 000001 activate Line loopback 000010deactivate Line loopback 000011 activate Payload/path loopback 000100deactivate Payload/path loopback 000101 activate Link loopback 000110deactivate Link loopback 000111 activate Client loopback 001000deactivate Client loopback 001001 Activate service 001010 Deactivateservice 001011 Set SRV-AIS 001100 Clear SRV-AIS 001101 Set SRV-RDI001110 Clear SRV-RDI

The activate-service command activates the service at the ESS. Inaddition, this command establishes the client link (i.e., between thecustomer equipment and the ESS). The deactivate-service command causesthe ESS to change its service configuration state to deactivated. Thedeactivate-service command also takes down the client link. For example,for an Ethernet service, the ESS can send an invalid 8B/10B code to thecustomer equipment or dispatch the appropriate Ethernet OAM frame. Theset-SRV-AIS and set-SRV-RDI commands take down the client link. Theclear-SRV-AIS and clear-SRV-RDI commands establish the client link. TheESS can establish the client link by initiating an auto-negotiationprocedure to the customer equipment. The service query command requeststhe ESS to respond with a service report.

When a service switch (either edge or core service switch) sends apriority message to an ESS, the service switch that sends the prioritymessage can determine that the receiving ESS has recongnized andprocessed the priority command by examining the service PRMs that theESS is dispatcing. For example, if a CSS sends a priority message to anESS for activating loopback, the CSS can examine the loopback-statusfield 256 (FIG. 9) in the service PRM of the ESS to verify that the ESSis in a loopback state.

The second type of command-and-response messages is message-orientedsignals. Message-oriented signals use a LAPD messaging format. Anexample of a message-oriented signaling format is Q.291/LAPD. FIG. 12shows an embodiment of a command message format 300. The format 300includes a two-bit message type field 304. Table 7 shows thecorresponding message type for each possible combination of bit valuesin the message-type field 304.

TABLE 7 Bit Message values Type 00 Reserved 01 Command 10 Response 11OAM

For command messages, the value stored in the message type field 304 isset to indicate a command. In one embodiment, the command message 306includes 57 bytes. The first and last bytes 302, 302′ are framedelimiters (storing a 7E hexadecimal value). The second byte (numberedas byte 1) has a 6-bit service access point identifier (SAPI) field 306,a one-bit command/response (C/R) field 310, and a one-bit an addressfield extension (EA) field 318. The next byte of the command message 300has a terminal endpoint identifier (TEI) 314 (set to zero) and anotheraddress field extension field 318 (set to zero).

The identity of the network element that originates the command messageoccurs in a 16-byte source-equipment-identifier (SEI) field 308. Acommand code stored in a 14-bit command-code field 312 identifies thetype of command and a 32-byte label stored in a service-identifier field316 denotes the service instance.

The command message 300 also has an FCS field 320. The ESS that producesa LAPD message generates the FCS and zero stuffing. For LAPD, zerostuffing entails inserting a zero after any sequence of five consecutiveones. Zero stuffing prevents the occurrence of a particular flag pattern(i.e., 01111110) in the bits between the opening and closing flags of aQ.291/LAPD frame. The receiver of the message removes a zero followingfive consecutive ones.

Table 8 below shows an exemplary set of commands codes corresponding tocommand codes stored in the command-code field 312. Fewer, more, ordifferent commands and bit value assignments can be used to practice theinvention.

TABLE 8 Command Code Command 000001 Service Query 000010 Client Status000011 Get Service ID 000100 Set Service ID 000101 Set Service State000110 Set Service Info 000111 Clear Service OMs 001000 Get Service OMs001001 Ping Request 001010 Trace Path 001011–11 . . . 1111 Reserved

Upon receiving a service query command, an ESS generates a servicereport in response. Service reports are response messages, the contentsof which are service specific. FIG. 13 shows an embodiment of anEthernet service report 330. Table 9 shows the various fields of theservice report format and the function of the fields.

TABLE 9 Field Function destination equipment identifier (DEI) identifiesthe destination network element of the response message serviceidentifier identifies the service instance message-type indicates thatthe type of message is response service type indicates that the type ofservice is Ethernet rate status Indicates the client interface rate atthe edge service switch (e.g., 10 M, 100 M, 1 G) service statusIndicates active or deactivated loopback status Indicates deactivated oractive client, link, payload or line loopback pause status Indicatespause status of service (enabled or disabled) duplexity status Indicatesduplexity status of service (Full or Half) committed information rate(CIR) 2-byte field indicates configured CIR at the edge service switch.Units are megabytes. peak information rate (PIR) 2 byte field indicatesthe configured PIR at the edge service switch. Units are megabytes.burst duration Unit (BDU) Indicates units of measure of burst duration(seconds, millisecond, or microseconds) burst duration Indicatesduration of client signal bursting. The 14-bit field permits more than16,000 burst duration units.

FIG. 14 shows an embodiment of a format for a Fibre Channel servicereport 340. The fields are similar to that of the Ethernet servicereport with the following noted differences. For the Fibre Channelservice report 340, the rate status field 342 indicates possible clientinterface rates of 100M, 1 G, or 2 G. For Ethernet, the options are 10M,100M and 1 G. Also, the Fibre Channel service report 340 includes aprovisioned buffer credits (PBC) field 346 to indicate the number ofbuffer credits provisioned at the ESS. It is to be understood that othertypes of services, such as an OC-n service, a DS-n service, and aManaged Wavelength (transparent) service, use similar fields as thosedescribed and fields that are unique to that service. Also, otherembodiments of the Ethernet and Fibre Channel service reports 330, 340can have different fields and functions than those described.

Generic Framing Procedure (GFP) Implementation of SMC

As described above, the SMC can also be implemented using clientmanagement frames of the generic framing procedure (GFP). A clientmanagement frame is a GFP frame containing information associated withthe management of the GFP connection between the GFP source and the GFPsink or with the management of the client signal. The GFP implementationof the SMC supports the service alarm indications (AIS and RDI) andservice performance monitoring described above. SMC capabilitiesunsupported by the GFP implementation include service monitoring by aCSS, non-8B/10B coded client services, and priority andcommand-and-response messages.

To support the AIS signal, the currently defined GFP CSF is used. TheGFP CSF can indicate a loss of client signal or loss of client charactersynchronization. To support the RDI signal, extensions to the GFP clientmanagement frame type definitions are provided. A user payload indicator(UPI) is defined for this purpose. TABLE 10 below defines the GFP clientmanagement frame payload uses for various UPI values. The particularpayload uses and UPI values described therein are for purposes ofillustrating the principles of the invention. One skilled in the artwill recognize that different payload uses and different UPI values thanthose described in Table 10 can be used to practice of the invention.

TABLE 10 PTI (Payload Type Indicator) = 100 UPI value Usage 0000 0000Reserved 0000 0001 Client Signal Fail (Loss of Client Signal) 0000 0010Client Signal Fail (Loss of Character Synchronization) 0000 0011 RemoteFault Indicator (RFI) 0000 0100 Service Performance Report (SPR) 00000101 through 1111 1110 Unused 1111 1111 Reserved

A GFP RFI is dispatched by an ESS in the upstream direction when a lossof GFP frame delineation is detected on the incoming optical signal.Each ESS dispatches a service PRM periodically (e.g., once per second).The GFP SPR is used to dispatch the service PRM and is formatted suchthat the Payload Type Indicator (PTI) equals 100 (in binary), the UPIequals 0000 0100 (in binary), and the Payload Length Indicator (PLI)indicates the number of bytes in the GFP payload area (which does notdenote GFP control frames). The GFP SPR client payload information fieldincludes fields for errored seconds (ES), severely errored seconds(SES), and service state (SS).

Examples of SMC Operation

The OBS framework of the invention can support various networkconfigurations. One such network configuration 10″ appears in FIG. 15.The network configuration 10″ is an example embodiment of the opticalnetwork 10 shown in FIG. 2. In this network configuration, a singlecarrier supports a service (e.g., an Ethernet Private Line service) overa single transport domain. Consider that customer traffic gains accessto the optical network 10″ and to the service at the ESS 14 through theclient interface 22. The traffic traverses the transport facility 26 tothe other service termination point, ESS 18, from which the traffic isdelivered to the customer through the client interface 28. Consider alsothat a network operator 348, who has access to the ESS 14 through acomputer system 348, desires to commission the service, but beforecommissioning the service desires to verify the connectivity of theoptical network 10″.

FIG. 16 shows an embodiment of a process 350 for commissioning a servicewithin the network and administrative domain of the single serviceprovider, of FIG. 15. At step 354, the network operator establishescommunication with the ESS 14. For the purpose of this example, theaccessed ESS is referred to as the near-end service switch and the ESS18 at the other end of the service is the far-end service switch. Thenetwork operator then causes a command message to be sent (step 358) tothe far-end switch 18 over the SMC 24 to deactivate the service.Similarly, a command message is sent (step 362) to the near-end serviceswitch 14. When the near-end and far-end switches receive the respectivecommand, each responds by setting its service state to deactivate and byinitiating shut down procedures for the client link. For example, eachservice switch can send an invalid 8B/10B code to shut down the clientlink. As a result, the service is deactivated.

At step 366, the network operator causes a command to be sent over theSMC 24 to the far-end service switch to activate payload loopback. Inresponse to the command, the far-end service switch enters a serviceloopback condition. Then the network operator transmits and monitors for(step 370) a test signal. If, at step 374, the test signal is receivedproperly, connectivity to the far-end SONET/SDH WAN facility isverified. The network operator then transmits (step 382) a command tothe far-end service switch 18 to deactivate the payload loopbackcondition. This causes the far-end service switch 18 to remove theloopback condition. If, at step 374, the test signal is not receivedproperly, the transport facility is ready (step 378) for thecommissioning of the service.

After connectivity is verified, the network operator transmits (step386) a service query command over the SMC to the far-end service switch.The far-end service switch 18 responds with a service report (here, anEthernet service report, see FIG. 10), which the network operator isable to monitor when received (step 390) at the near-end service switch14. Similarly, the network operator issues (step 394) a service querycommand to the near-end service switch 14 and receives (step 398) aservice report produced by the near-end service switch 14 in response.From the service reports, the network operator determines (step 402)whether both ends of the service are consistently provisioned (i.e.,configured). If the provisioning is inconsistent, the WAN facility isunprepared (step 406) for the commissioning of the service. If theservice reports show consistent provisioning, the network operatortransmits (steps 410 and 414) a command over the SMC 24 to the far-endservice switch 18 and another command to the near-end service switch 14to activate the service. In reply, each switch 14, 18 changes (step 418)its service state to activated and establishes a client link (e.g., byinitiating auto-negotiation procedures). The Ethernet Private Lineservice is thus prepared for Customer traffic.

FIG. 17 shows an embodiment of a process 450 for diagnosing servicedegradation in a network and administrative domain of a single serviceprovider, of FIG. 15. At step 454, a network operator accesses one ofthe ESSs 14, 18 and monitors the service-status field 204 of the SMC 24(in one embodiment, the Z3 byte of the POH). For the purpose of thisexample, the accessed ESS is referred to as the near-end service switchand the ESS at the other end of the service is the far-end serviceswitch. Consider that the service-status field 204 of the POH byteindicates a degradation of services (step 458). Then, the networkoperator sends (step 462) service-query commands to the near-end serviceswitch and to the far-end service switch over the SMC 24. In response tothe commands, each ESS 14, 18 produces (step 466) a correspondingservice report message.

From the service reports, the cause of the service degradation isdetermined (step 470). For example, the network operator discovers thatthe far-end packet drop count is excessive and that the cause is thatthe near-end CIR is misconfigured: the CIR of the near-end serviceswitch exceeds the rate status of the far-end service switch.Accordingly, the network operator takes (step 474) appropriatecorrective action, such as deactivating and reconfiguring the service.

FIG. 18 shows another example of a process 500 illustrating a diagnosticcapability provided by the SMC of the invention. In the process 500, aservice provider is able to proactively institute corrective action inresponse to indications that its service is degrading. This exemplaryprocess is described in the context of a network and administrativedomain of a single service provider, of FIG. 15.

Consider that in the process of monitoring PRMs generated by the ESSs14, 18 and transmitted over the SMC 24, the service provider notices(step 504) that a service alarm has been raised. To investigate further,the service provider sends (step 508) a command (e.g., a service-querycommand or a get-service-ID command) to the ESS that raised the alarm.The ESS receiving the command produces (step 512) a response (i.e., aservice report) that has the service identifier. The service providerreceives (step 516) the response and correlates (step 520) the serviceID to a path ID associated with the dedicated circuit supporting theservice. From the path ID, the service provider identifies (step 524)the customer(s) that may be affected by a degradation of the service.For the purpose of these correlations, the ESS's maintain databases ortables that associate service IDs with paths IDs and path IDs withcustomers. Accordingly, the service provider takes (step 528) proactivecorrective action to remedy or mitigate the condition causing the alarmor to alert the customer of the potential problem with the service, orcombinations thereof.

The various processes 350, 450, and 500 described above are examples ofcapabilities given to service providers to manage their service. Theseexamples and other capabilities are not limited to single serviceproviders or to single transport domains. FIG. 19 shows another exampleof a network configuration 10′″. In this network configuration 10′″,multiple carriers support a service (e.g., an Ethernet Private Lineservice) over multiple transport domains. Consider that customer trafficgains access to the optical network 10′″ and to the service at the ESS14 through the client interface 22. The traffic traverses the transportfacility 26 of Metro Carrier A to the CSS 18′. Through a networkinter-connect device (not shown), the CSS 18′ hands-off the customertraffic to the transport facility 26′ of Long Haul Carrier B. Thetraffic passes to a CSS 18″, then over the transport facility 26″ ofMetro Carrier C to the other service termination point, ESS 18. Thetraffic is then delivered to the customer through the client interface28. This network configuration 10′″ represents a typical scenario inwhich Metro Carrier A and Metro Carrier C are private line wholesalers,and Long Haul Carrier B is a private line retailer. Using the SMC, allcarriers can monitor the end-to-end service status (e.g., active,degrade, or failure). In general, any of the carriers can gather servicestate information, even if the ESS 14, 18 is not part of that carrier'snetwork.

Consider that a network operator, who has access to the CSS 18′ througha computer system 550, desires to commission the service across thenetworks of the three carriers. FIG. 20 shows an embodiment of a process600 for commissioning the service across multiple carrier networks. Forthis example, consider also that Metro Carriers A and C allow Long HaulCarrier B to perform “passive” and “non-passive” SMC operations withintheir networks. Passive SMC operations are those that request servicestate information, but do not change any service state information.Non-passive SMC operations change service state information.

To commission the service, the network operator at carrier B sends (step604) commands over the SMC to both ESS 14, 18. When each ESS 14, 18receives its respective command, each responds by setting its servicestate to deactivate and by initiating shut down procedures for itsclient link. Then, the network operator sends (step 608) a command overthe SMC 24 to the ESS 18 in the carrier C network to enter the payloadloopback condition. In response to the command, the ESS 18 enters aservice loopback condition. The network operator then transmits andmonitors for (step 612) a test signal. If, at step 616, the test signalis received properly, connectivity to the ESS 18 facility is verified.The network operator then transmits (step 620) a command to the far-endswitch 18 to deactivate payload loopback, which causes the far-endswitch 18 to remove the loopback condition. If the test signal is notreceived properly, the WAN facility is unprepared (step 618) forcommissioning the service. The network operator can then similarlyverify (step 622) connectivity to the ESS 14 of Metro Carrier A.

After connectivity is verified, the network operator transmits (step624) a service-query over the SMC to each of the ESSs 14, 18. Each ESS14, 18 responds with a service report, which the network operatorreceives (step 628) at the CSS 18′. The destination equipment identifierin each service report identifies the CSS 18′ as the destination serviceswitch.

The network operator at the CSS 18′ determines (step 632) from thereceived service reports whether both ends of the service areconsistently provisioned (i.e., configured). If the provisioning isinconsistent, the WAN facility is not ready (step 618) for thecommissioning of the service. If the service reports show consistentprovisioning, the network operator transmits (step 636) a command overthe SMC 24 to the ESS 18 and another command to the ESS 14 to activatethe service. In reply, each ESS 14, 18 changes (step 640) its servicestate to activate and establishes a client link (e.g., by initiatingauto-negotiation procedures). Consequently, the service is prepared tocarry customer traffic.

While the invention has been shown and described with reference tospecific preferred embodiments, it should be understood by those skilledin the art that various changes in form and detail may be made thereinwithout departing from the spirit and scope of the invention as definedby the following claims.

1. A network element connected at one end of a dedicated circuit used tocarry customer traffic associated with a service, the network elementcomprising: a client interface receiving client signals from a clientnetwork; a service management channel entity deriving from the clientsignals service-specific information related to a performance of theservice and generating a message in response to the service performanceinformation, the message identifying the service to which the serviceperformance information in the message pertains; and a transportinterface for mapping and adapting the client signals to an opticaltransport facility, the transport interface transmitting the message toa network element at the other end of the dedicated circuit over aservice management channel capable of carrying the message across anetwork-to-network interface.
 2. The network element of claim 1, whereinthe service management channel includes a byte of a path overhead of anoptical transmission frame.
 3. The network element of claim 2, whereinthe optical transmission frame is a Synchronous Optical Network (SONET)frame and the byte of the path overhead is a Z3 byte.
 4. The networkelement of claim 2, wherein the path overhead byte has bits forconveying a status of the service and bits for conveying the message. 5.The network element of claim 4, wherein the path overhead byte furthercomprises bits for conveying commands and responses.
 6. The networkelement of claim 1, wherein the service management channel includes aheader in a Generic Framing Procedure client management frame.
 7. Thenetwork element of claim 6, wherein the header includes a payload typeindicator (PTI) field and a user payload indicator (UPI) field, andwherein the header indicates that the Generic Framing Procedure clientmanagement frame contains the message when the PTI and UPI fieldscontain certain predefined values.
 8. The network element of claim 1,wherein the message is one of a command message, a response to a commandmessage, a service performance report message, and a priority codemessage.
 9. The network element of claim 1, wherein the service is oneof an asynchronous service, a synchronous service, a local area networkservice, a storage area network service, and a managedwavelengthservice.